The overall goal of this project is to understand the light scattering properties of single biological cells. The precision with which changes in cell morphology can be measured with light scattering in flow cytometers will be evaluated and optimized so that light scattering can become a more useful tool for cell analysis in the clinical laboratory. The specific aims for the current year include 1) use of the multiangle light scatter flow cytometer to study mitogen stimulation of mononuclear cell cultures, and 2) theoretical modelling studies of current and proposed detector configurations to determine their sensitivity to small changes in cell and nuclear diameters and refractive indices.